For any rotating system requiring lubrication it is essential to have the oil or lubricating fluid enter at the smallest inner radius possible. This is because centrifugal force causes whatever fluid is emitted to the center of the rotating system to flow towards the outer portions of the system. U.S. Pat. No. 1,184,609 represents the basic technique.
In a differential planetary transmission, planet gears (compound type) are mounted in or on a rotating carrier assembly which itself is supported by a set of bearings. A sun gear at the interior of the carrier drives the planetary gears. With the exception of an opening for the sun gears, the ends of the carrier are typically closed to provide structural support for the planetary gears and to accommodate the bearings which support the carrier. Accordingly, lubricating fluid cannot be injected into the rotating assembly from the ends of the carrier and into the sun gear meshes (cf. U.S. Pat. Nos. 3,230,796; 3,065,822; Japan No. 56-35860; East German No. 146,327; and U.K. No. 259,222). Lubricating fluid cannot be efficiently injected from an external source beyond the diameter of the rotating assembly because of the action of centrifugal force. Centrifugal force limits the degree of penetration of the lubricating fluid sprayed directly on the rotating system. If penetration were attempted by spraying oil from an external diameter, the oil pressure or lubricating fluid pressure would have to be very high to counteract the effect of centrifugal force. High pressure lubricating systems are expensive, not only from a first cost point of view, but also from a maintenance and operating cost point of view. Moreover, if lubricating fluid could be injected from one end of the carrier, or through an opening in the carrier between the planetary gears, it would enter on an intermittent basis since the carrier itself is rotating. Thus, it is difficult to design an efficient, effective, low cost lubricating system for a planetary transmission.
There have been several attempts by others to supply lubricating fluid to the interior of a rotating geared shaft from a source on the periphery of the shaft (i.e., U.S. Pat. Nos. 1,299,156 and 2,926,755). However, there are added difficulties when the transmission shaft is a thin-walled quill shaft which is directly driven by a steam turbine operating at optimum velocity ratios and at the highest possible efficiency (e.g., 20,000 RPM). In addition, if the transmission is driven by a shaft which is not supported by journal bearings, lubricating fluid must not only be made to somehow enter the shaft from a position intermediate the ends of that shaft, but also lubricating fluid must be transferred to the interior of that shaft without any direct mechanical or fluid coupling (cf., U.S. Pat. Nos. 1,299,156 and 2,926,755). Thus, a modern innovative and preferably practical approach to an otherwise basic design problem is needed.